The present invention relates to a new and improved construction of a control apparatus for controlling a feed or advance movement of a tool relative to a workpiece in a gear cutting machine operating according to a continuous cutting process.
Generally speaking, the control apparatus of the present development is of the type comprising a drive for the tool and the workpiece and a hydraulic directional control valve containing a slide or spool which controls the infeed of pressurized fluid medium to a feed or advance piston. By means of the feed movement of the feed piston there is moved through a preparatory path which can be adjusted at a control cam carrier or support and also through a machining path which is governed by the control cam.
Control apparatuses for controlling the feed or advance motion of a tool in a gear cutting machine insure that the tool moves, throughout a preparatory path, relatively quickly, and then during a machining path, on the other hand, relatively slowly in the direction of the workpiece.
There are known to the art control equipment of the type generally discussed above, wherein the length of the preparatory path must be adjusted. This adjustment or setting must be undertaken each time for each newly employed tool or workpiece and is dependent upon the spacing between the tool and the workpiece in a starting position. This setting is accomplished at the control apparatus in that, in the starting position this spacing also is adjusted between a control cam and a feeler or follower roll.
Now if for some reason this spacing between the tool and the workpiece has been incorrectly set at the control apparatus, then considerable damage can arise at the gear cutting machine and also at the tool and the workpiece, in that the rotating tool still penetrates into the likewise rotating workpiece during the preparatory path. This in turn causes intensive pressure increases in the hydraulically operating portion of the control equipment. The resultant high forces between the tool and the workpiece lead to its damage or destruction, as the case may be. Additionally, damage to the bearings and guides of the movable parts of the machine is equally possible, and the elimination thereof is extremely costly.